Police in Aurora, Colorado spent the weekend disarming a snarl of bombs and incendiary devices inside the apartment of James Holmes. He's the man police arrested early on Friday, just after they say he opened fire in a crowded movie theater, killing 12 people and injuring 58. Holmes is described as a 24-year-old who'd been studying at the University of Colorado. He's expected in court later this morning.

And we're going to talk about this with Megan Verlee of Colorado Public Radio. Welcome to the program.

MEGAN VERLEE, BYLINE: Hi, Steve.

INSKEEP: What did police learn from searching this man's apartment once they got in?

VERLEE: Well, certainly, they're learning more about the devices he left in there, and they seem to be getting angrier. The apartment was set up with a tripwire right in front of the front door that, if it were actually live, would have tripped the explosions. And police believe it might have been set up for one of their own coming after the shooting to investigate.

It looks like there are about 30 bottles of explosive liquid, about 10 gallons of gasoline, and then bullets and all sorts of stuff put together into homemade grenades that could have potentially caused an inferno in that apartment, and even further into the apartment building.

INSKEEP: So you get a picture of this man assembling his arsenal for the attack, making elaborate plans for the attack, and then putting one more thing after another inside his apartment. Who is this guy, as best as police can determine?

VERLEE: Well - and it's becoming an eerily familiar phrase. He's a quiet guy who didn't seem to have many close friends or acquaintances, certainly here in Colorado where he moved a few years ago. We're hearing that he is very academically brilliant, top of his class at his university in California. And that - as reporters have met more and more people who knew him - seems to be, I guess, the defining feature of James Holmes, the suspect, that he's a very smart, very quiet guy and - as you all too often hear after events like this - someone no one thought capable of something like this.

INSKEEP: Now, I know there's very little of a criminal record that's been found on this man. But there is there any other indication of psychological trouble or other kinds of trouble that turned up?

VERLEE: Well, I think the most disturbing - or one of the most disturbing details that came out this weekend was from the owner of a shooting range east of Aurora. He says that James Holmes tried to apply to become a member there fairly recently. And when he tried to call Holmes back to invite him to a mandatory orientation meeting, the voicemail greeting that he ran into on Holmes' phone was apparently very incoherent and almost disturbing sounding.

And so this gentleman warned his staff that if Holmes came to the orientation, to alert the shooting range owner and not to let homes become a member. It's the first indication we're getting of his state of mind.

INSKEEP: And I suppose that if that is the case - and, of course, we're talking about allegations, here, at this point - one question is going to be: How long was he like that? How many other people noticed something strange?

VERLEE: The University of Colorado, where he was in the process of withdrawing from, has been very, very tightlipped about their relationship with Holmes and what they had experienced with him in recent months. All they're saying is that he withdrew, that it was a very standard process. But they're actually explicitly telling people who worked there not to talk about Holmes - if they knew him, or even if they didn't.

INSKEEP: OK. Now, how is the community responding to all of this - Aurora, Colorado?

VERLEE: It's been hard. This is making the community pull together. This has touched everyone to their core. But I've also talked to a lot of people who are really shaken by this. There's been a fair amount of other violence this summer, increasing gang violence. There's a Denver policewoman killed at a music festival that really, I think, shook a lot of people across the metro area.

And so, there are people I've talked who say this is, you know, an event beyond the pale and something we never imagined. But it is coming after all these other shootings and other painful events this summer. And so, in a way, it feels like a continuum of violence. And it feels like it's just been a very hard summer in that city.